According to the documents, the NSA and its British counterpart, GCHQ, are using the small tracking files called cookies that advertising networks place on computers to identify people browsing the internet. The intelligence agencies have made particular use of the “PREFID”, part of Google-specific tracking software known as the “PREF” cookie.AdvertisementThis cookie typically doesn’t contain personal information, such as someone’s name or email address, but it does contain numeric codes that enable websites to uniquely identify a person’s browser.In addition to tracking web visits, the PREFID allows the NSA to single out an individual’s communications among the sea of internet data in order to send out software that can hack that person’s computer.
via NSA uses Google cookies to find targets for hacking, spying.